There is going to be some difference. It will be due to the way you hold your eye to the scope versus hers. The difference won't be that great-- it won't put the point of aim off the paper-- but there will be a change.
My advice is to do exactly as you are doing, but make sure she has a chance to zero the rifle herself after the start of season. Before then, have her use discretion in making longer shots. If you sight in at 100 yards, she should be good out to at least 50 in a worst case. The closer your eye position matches hers will determine how much better it is.
I frequently work with KYHillChick's "Voice of God." She likes to shoot milk jugs at 400 yards-- she said the Lord told her to do it. I don't argue. It's a 30-06 bolt gun. We'll take turns shaking it out before she goes for the distance shots. She may be grouping at 4 O'Clock 4 inches off the bull, I may be at 10 O'Clock 2 inches off the bull.
This is similar to what happens when your rifle and ammo don't arrive in the same spot, or the ammo is left behind on the counter at home. You go to the store and you're shooting Remington 150'sand all they have is Winchester 180's. It's going to be close. You probably can go out and hunt opening morning without sighting in. Distance? That's between you and your conscience, but I'd think inside 50 yards you'd have a deer.
For all the derision we heap on guys who have their new rifles bore-sighted the night before season, there actually is some logic to it. If you bore sight a rifle, chances are you're at least on the paper at 20 yards. That's why we bore sight them. As long as a hunter doesn't take but a 40 yard shot, then probably he's going to get a deer with that rifle. The problem comes from trying to extend that out to 200 yards offhand, and doubling the problem by doing it with a 30-30. (see my recent discussion of the Maysville Walmart)